How to Test for Mold Toxicity: Urine vs. Blood Testing Explained
There are two very different types of mycotoxin tests floating around the functional medicine world right now, and I see people get confused about this constantly. Which one actually tells you if you have mold toxicity? What is each one measuring? And why does it even matter which one you choose?
So in this article, I'm breaking down the difference between the two most popular mold toxicity tests — what each one tells you, where each one falls short, and how to figure out which is the right fit for where you're at in your health journey.
This content is for educational purposes only and does not diagnose, treat, or cure any condition. Always consult a licensed healthcare provider.
What Are Mycotoxins, and Why Are They So Hard to Pin Down?
Mycotoxins are the toxic metabolites that mold spores release — not the mold itself. These are the chemical byproducts that actually cause the damage and the symptoms you're probably dealing with.
They're invisible. They're odorless. You can't see them or smell them. But they can stay in your body long after you've left a contaminated environment.
This is something I see all the time: someone isn't currently exposed to mold, but they were a year or two ago. Because the mycotoxins were never fully detoxed, they're still dealing with symptoms now.
The most common ways you get exposed:
- Inhalation — breathing it in
- Ingestion — consuming it through contaminated food
- Skin absorption — absorbing it directly
Why Mold Testing Gets So Complicated
Not everybody detoxes or excretes toxins the same way — especially people with the HLA-DR genetic variant, which makes it significantly harder for the body to successfully clear mycotoxins.
Does that mean you need to run out and get an HLA genetic test right now? Not necessarily — it's not going to change a whole lot other than confirming that you need the right protocol and the right support to heal.
What it does explain is why two people with identical exposure can end up with completely different lab results. It's not about the environment alone — it's about that individual's immune system, genetic pathways, and detox capacity. This is also why two people can live in the same home or work in the same building, and one person feels like they're dying while the other feels totally fine. You have your own biochemistry.
One important note: neither blood nor urine mycotoxin testing is FDA-approved to technically diagnose mold illness. These tests are tools to help you get to the root cause of what's driving your symptoms — not a formal diagnosis.
Urine Mycotoxin Testing: What It Shows and Where It Falls Short
This is the test I personally prefer, so let me walk you through how it works, what it's good for, and its limitations.
What it measures: Urine mycotoxin testing measures the metabolites your body is actively excreting and detoxing through the kidneys. Many mycotoxins are hard on the kidneys because of how they affect the immune system and detox pathways.
How it works: There are several companies that offer this test — the one I use and have had the most success with is Mosaic Diagnostics. It's simple: you get a kit shipped to you, collect a urine sample first thing in the morning, and ship it back to the lab for a full panel.
Why I like it: It's non-invasive, easy to do at home, and genuinely useful for tracking progress through a detox protocol. When I first ran mine, I had certain mycotoxin strains show up at a certain level. As I moved further into my own detox protocol, those numbers actually went up — and that was a good sign. It meant my body was actively and successfully pulling toxins out that had been stored elsewhere.
If your numbers go up after starting a detox protocol, that's very normal. A lot of mycotoxins get stored in fat tissue and cells throughout the body, so seeing higher levels once you start pulling them out is a sign of progress, not a setback.
Limitations to know:
- It can't tell you whether the source is food or a water-damaged building — it won't help you pinpoint where in your environment the exposure is coming from.
- It only shows recent excretion, not your total body burden. It captures what your kidneys are currently filtering, not what's stored in tissue, organs, or blood.
- False negatives are possible. If you're dealing with something like CIRS (chronic inflammatory response syndrome) or a very high toxin burden, your body may not be efficiently clearing toxins — which means you could show low urine levels even with a high body burden. I've had clients who were clearly dealing with mold, tested negative on urine, started a detox protocol anyway, and then began flushing mycotoxins out.
Blood Mycotoxin Testing: What It Shows and Where It Falls Short
Blood testing is common too, and it's measuring something different entirely.
Serum mycotoxin antibody testing (IgG/IgE): This measures your immune system's antibody response to mycotoxins — not the mycotoxins themselves. IgG tends to reflect past or ongoing chronic exposure, while IgE reflects more of a current allergic response.
The upside of blood testing is that it can show both current and historical exposure. The limitation is that it's measuring immune sensitization, not what your body is actively excreting.
Shoemaker protocol markers: This is a separate category of blood markers — things like C4a, MSH, ACTH, cortisol, and leptin. These aren't directly testing for mycotoxins. Instead, they measure how your body's inflammatory and immune response is reacting to biotoxin exposure. If you're trying to work through a CIRS diagnosis specifically, these markers can help build a clearer picture of which systems are most affected and where your protocol needs adjusting.
Urine vs. Blood: Which Test Is Right for You?
Here's the core difference: urine testing asks what toxins your body is currently excreting. Blood testing asks what mold exposure is currently doing to your immune system. Two different questions — both potentially useful, but not necessarily both required.
Urine testing tends to be more helpful when:
- You want to identify specific mold species you may be dealing with
- You've already cleaned up your diet (contaminated coffee, poorly stored grains, and other mycotoxin-heavy foods can otherwise skew your results)
- You want to track how well your body is excreting toxins over the course of a protocol
Blood testing tends to be more helpful when:
- You want to know whether mold exposure has triggered an actual immune response
- You want to understand which body systems are most impacted and need the most support
- You're unsure whether you're dealing with current or past exposure
You don't have to choose only one — the most complete approach combines both. It's also worth mentioning two related tests that can round out the picture:
- ERMI or HERTSMI testing — air and dust sampling to identify mold in your actual environment
- HLA-DR genetic testing — if you're curious about your genetic susceptibility to detoxing mold effectively
My Approach
Personally, I don't run the full Shoemaker panel or every available biomarker. I primarily use urine mycotoxin testing, paired with a few supporting markers I've found genuinely useful — hsCRP, a full hormone panel, and EBV reactivation testing.
Which combination is right for you really depends on your specific situation and what your integrative or functional health practitioner recommends based on your protocol.
I won't sugarcoat it: mold testing can be time-consuming, expensive, and frustrating. But if you're patient and willing to go through the right steps — proper testing, proper protocol, proper pacing — your body can heal. Your energy, your immune system, and your overall health absolutely can come back.
If you want to understand one of the most commonly missed mycotoxins in more detail, read more on Ochratoxin A — the hidden mold toxin destroying your immune system.
If you want to go deeper on identifying and detoxing from mold safely, The Mold Healing Blueprint walks through the full step-by-step process I used to heal — and the same one I use with clients.
If you're ready to run the actual testing discussed in this article, you can find the Mycotoxin (Urine) Test I use and recommend here.
Ready to Get Real Answers Instead of Guessing?
If you've been bouncing between doctors, running basic labs that keep coming back "normal," and still feeling like something is off — testing the right way is where real answers start.
Healing is possible when you focus on healing the root cause. I'd love to help you get your health back on track! -Ashley Drummonds
